The design of the Capture / Compare Unit (CCU) of the C504 microcontroller allows
generation of 7 digital output signals without CPU load. A set of Special Function
Registers (SFR, see corresponding tables in C504 User’s Manual) offers to the users
extreme flexibility to choose of possible waveforms, such as pulse width modulation
(PWM). By appropriate setting of SFRs, frequency (period register), duty cycles (compare
registers) and active / passive levels (COINI register) of output signals can be easily
controlled.
These features should be used with respect to the application, e.g. motor control using
three phase transistor inverters with automatic dead time generation by the CCU. The
dead time is implemented with a 16-bit offset register. In order to generate correct output
pulse patterns for three phase transistor inverters, passive levels for highside switches
must be inverted compared to those of lowside switches.